Feature: Other shells

Make update whitelist command work for non posix shells

I know at least one person who uses a non-posix shell.

They asked that the command be wrapped such that it invokes sh/bash (or potentially that it just be written in perl -- just so long as it doesn't fail when copied into their non-posix shell).

Released in 0.0.16-alpha -- it appears to work for fishshell.

⚠️ I don't actively test support for non-posix shells, so this probably will break periodically. I'm still thinking through the best approach for this. One is to offer a client that's responsible for consuming this output, another is relying on talk-to-the-bot.

At some point, I might add a test-suite to make sure this feature doesn't break, but it isn't high on my todo list.